Coronavirus could end up going global

By HELEN BRANSWELL The Canadian PressPublished March 30, 2013 - 9:44am Last Updated March 30, 2013 - 9:52am

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Trajectory depends on prevalence of patients called superspreaders

A coronavirus is shown in this colourized transmission electron micrograph. The World Health Organization says it has been notified of another coronavirus infection the 15th since the virus came to light last fall. The case was discovered in Saudi Arabia, which has reported the most cases of any country to date.(BETH FISCHER / US National Institute for Allergy and Infectious Diseases)

TORONTO — People who think the new coronavirus couldn’t take off and cause a SARS-like crisis may have forgotten a phenomenon that was a game-changer during SARS — patients called superspreaders.

At present, this new coronavirus doesn’t seem to spread easily from person to person, a fact which some people use to argue it will not become the next SARS. Some limited human transmission has occurred, but confirmed cases are few and sporadically seen.

However, several experts suggest that superspreaders, which turned SARS into a global outbreak, could do the same with this new virus. That term refers to people who buck the transmission trend with a given bacteria or virus, infecting many more people than is the norm.

Dutch virologist Ron Fouchier gives a succinct answer when asked if a superspreader could profoundly alter the pattern of spread with this emerging virus: “Yes.”

If the virus infected someone who turned out to be a superspreader, and that person sought care in a hospital that wasn’t taking precautions against novel coronavirus infections, this new disease could rapidly begin to resemble SARS.

“I think we would be in big trouble,” says Fouchier, who is with Erasmus Medical Centre in Rotterdam. “There were really only very few cases that caused the trouble during the SARS outbreak.”

So far there have been 16 confirmed infections with the new virus, 10 of which have been fatal. Cases have emerged from Saudi Arabia, Qatar and Jordan.

After the dust settled from the whirlwind 2003 event and infectious diseases teams traded their emergency response vests for their research coats, it became apparent that the SARS coronavirus hadn’t spread very well.

In fact, most people who contracted the virus either didn’t infect anyone else, or passed it on to a single person. With that kind of inefficient transmission, an outbreak would normally stall, lacking the momentum to keep itself going.

But during SARS, a select few people inexplicably ended up infecting a dozen, two dozen or more people, turning a disease that might otherwise never have been spotted into a four-month worldwide panic.

SARS went global thanks to a superspreader — a Chinese doctor who infected more than a dozen people at a Hong Kong hotel in late February. One of those people brought the virus to Canada.

In Singapore, one SARS patient infected 62 people. In Toronto, which had several superspreaders, one early case infected 44 others.

In fact, an elderly couple who contracted the virus on the night SARS made its first appearance in a Toronto hospital were both superspreaders.

The woman, who had taken her husband to hospital for a heart problem, brought him back a few days later when he began to suffer from the symptoms that would come to be recognized as SARS. Later, people who traced the spread of the virus through Toronto hospitals would see that she infected three admission clerks, a security guard, five visitors, three nurses and one housekeeper — all within a 21/2-hour span.

“She wasn’t that sick, actually. I don’t even know if she had a fever,” says Dr. Donald Low, the Toronto microbiologist who helped lead the city’s SARS response.

“But clearly she was excreting a lot of virus … which then ping-ponged into a massive number of cases throughout the city.”

It’s not clear why some people became superspreaders during SARS.

True, in some cases the amplified transmission seemed to relate more to the circumstances than actual patient. For instance, it became apparent that intubating a patient — putting him or her on a breathing machine — could be a superspreader event if health-care workers weren’t wearing respirators fitted over their noses and mouths and goggles to shield the mucus membranes around their eyes.

Still, there were some people who seemed to spew more virus than others. Why? Maybe it was due to their health status — perhaps they had another medical condition that amped up the amount of virus they emitted, muses Michael Osterholm, director of the Center for Infectious Diseases Research and Policy at the University of Minnesota.

Osterholm thinks it could happen again. “Is there a potential here for a superspreader to be in our midst? I think absolutely. Yes.”

“It’s the virus and the host and the environment here all interacting. And any one of them could up the ante for widespread transmission. This is why it’s kind of a stay-tuned (situation),” Osterholm warns.

Low too thinks it’s a possibility.

“These RNA viruses, you just can’t predict what they’re going to do,” he says. (Coronaviruses are RNA viruses, which mutate rapidly.) “So the longer they stay in the human population, the more likely it is they’re going to do something that’s not good.”